Present-Day Dynamics of Flood Hazard Characteristics in Rivers in the North Caucasus, Russia

The present-day dynamics of maximal water levels was evaluated, and space and time variations of level excess during unfavorable and hazardous events in North Caucasian rivers were analyzed. The study was based on data from 59 hydrological gages over period 1961–2017. The mathematical expectation of maximal water levels was found to increase everywhere from 1961–1990 to 1991–2017, and the increase in the variance was also a dominating trend in North Caucasian rivers. In the period under consideration, water levels of unfavorable and hazardous phenomena were exceeded by maximal water levels on the average in 19.3 and 10.6% cases, respectively. At some sections, this characteristic reached 93.2 and 88.6%, respectively. The marks of unfavorable and hazardous phenomena in the Kuban basin and in rivers of the Caucasian Black Sea coast was found to increase between 1961–1990 and 1991–2017. In rivers in the Terek and Kuma basins, the numbers of gages where the marks of unfavorable phenomena increased or decreased were the same; however, from 1961–1990 to 1991–2017, dominating are gages with a tendency toward a decrease in the number of cases with levels above the marks of hazardous phenomena.